Brian O'Driscoll's preparation for Leinster's Heineken Cup tie will not have been helped by being deposed as Ireland's captain. Photograph: Ken Sutton/Colorsport

This will make you feel old: somehow we have already reached the 10th anniversary of the famous "Miracle Match" between Munster and Gloucester at Thomond Park. Those of us lucky enough to have been present can still hear the disbelieving cries as the visitors were shredded 33-6.

And now, as so often, life has come full circle. The heroes of 2003 are a decade balder and greyer but, once more, Irish teams are back wrestling the odds in Europe. Both Munster and the defending champions Leinster could be elbowed sideways into the Amlin Challenge Cup this weekend if they cannot conjure four-try wins against Racing Métro and Exeter Chiefs respectively. Even then, other results must go in their favour. It is 15 years since the Heineken Cup quarter-final draw contained neither of the two Irish provincial grandees.

Considering Leinster's recent title-winning excellence, this has a distinctly alien feel to it. To make matters worse, there are still fears that the Irish fly-half Jonathan Sexton will leave or Racing Métro at the end of this season despite the denials of the French club's owner, Jacky Lorenzetti. Brian O'Driscoll has just been deposed as national captain and is entering the final furlong of his thoroughbred career. His old midfield colleague Gordon D'Arcy is 33, Leo Cullen turned 35 last week and the All Black lock, Brad Thorn, so valuable last season, has gone. A changing of the garda is already under way.

If the outstanding coach Joe Schmidt returns home to New Zealand next year, as many also anticipate, Leinster could find themselves pretty much where Munster are now. As with Leinster and O'Driscoll, the absence through injury of their talisman Paul O'Connell has shone a harsh light on the next generation. Some look promising enough but replacing Anthony Foley, David Wallace, Alan Quinlan, John Hayes, Denis Leamy and Jerry Flannery was never likely to be a routine assignment.

"If you look at the players Munster have lost over the past three to four years, a huge amount of experience has gone," says Tom Hayes, brother of John and the influential captain of Exeter. "For a lot of people who have only been supporting Munster for the last 10 years, it would be a big shock to see them not get out of the group. But these things happen. They've got a new coach trying to implement a new style of play. These things take time."

In the view of Hayes and most others we are talking an Irish hiatus rather than a Cliffs of Moher-scale fall.

Ulster have been having a fine season and Leicester's Geordan Murphy, a long-time colleague of all the leading Irish players, reckons there is life in the old dogs yet. "I just think it's a blip. If O'Driscoll and O'Connell had been playing more often, it might be a different story even though they are older. Some of those great players still have a lot to add. I'm excited about the next couple of years for Irish rugby … if you take out O'Driscoll, D'Arcy and O'Connell, you've got a team who are mostly in their mid-20s and could be around for six or seven years more. It's not all doom and gloom, especially if we go out to try to play with a high intensity. I was really enthused by the way we played against Argentina in November. If we do that again I'm quietly hopeful for the Six Nations."

Hayes also stresses that Leinster, in particular, tend to be stronger from January onwards, with all their preparations geared towards peaking at the season's business end. "It's been fairly noticeable in the analysis we've done that the intensity of their rugby has lifted over the last few weeks," Hayes says. "A lot of their players are looking towards a big Six Nations and this is the time of the year when they really start to crank things up. When we played them in the opening round they were a little bit undercooked. It's probably going to be a different story this weekend."

Maybe, maybe not. There are plenty in Ireland concerned about the tighthead prop situation below Leinster's Mike Ross, with the hastily imported Irish Kiwi Michael Bent yet to show he is an irresistible force.

Sexton is an eye-catching talent but the Racing Métro offer is substantial enough to distract anyone. "If the numbers are right, it can't not happen," predicted one experienced Irish insider this week.

There is also the age-old problem faced by all champions with a title to defend. "They say it's hard to get to the top but it's harder staying there," Hayes says. "When you're up there everyone wants to knock you off."

Leicester have been through a similar period of everyone chasing their tail and Murphy confirms the experience can be sapping. "It's incredibly difficult. If you're in any way below par you're going to be under pressure. Leinster were obviously a bit shell-shocked at home to Clermont and losing that game means they're up against it."

Pin Murphy into a corner and he predicts a four-try Leinster victory at Sandy Park on Saturday. "It's a tough place to go but they'll fancy their chances. They'll throw everything at it and I'd expect them to get a bonus point." He is less confident about a Ronan O'Gara-less Munster at home to Racing on Sunday. "I think Munster have a tougher task. People in Ireland are already reminiscing about the Miracle Match but Racing are no mugs. It'll be a big ask."

Hayes, as a son of Co Limerick, will be even more intrigued to see what happens. In 2003 he opted to stay at home and watch the Gloucester game on television but "I went out and joined the celebrations afterwards all right."

This time he will demand Exeter complicate life for their visitors from Dublin, miracles or no miracles. "You can't say Leinster are done and dusted as a side when they've won the Heineken Cup for the last two years. They're still in with a chance of getting out of the pool … you can't say they're finished. We're certainly not looking at it that way."